1. Field of the Invention
The invention relates to a method for generating output calibration response characteristics of crash sensors, including those used in vehicle collision tests.
2. Disclosure Information
Many vehicles are equipped with passenger restraint systems incorporating an air bag for protecting vehicle passengers in the event of a crash. In order to deploy the air bag at the proper time, it is known in the art to employ specialized sensors and associated circuitry for detecting a crash event that may threaten an occupant""s life so as to release the air bag at the appropriate time. In order to be effective, the passenger restraint system must be able to separate crash events which would require deployment of the air bag, and those crash events in which deployment of the air bag would be unnecessary or undesirable.
For example, it is known to measure the dynamic response characteristics of a prototype crash accelerometer wherein the accelerometer to be tested is fixed to a vehicle and the vehicle is crashed. The crash can produce an impulsive wave impinging on the accelerometer, thus generating an electrical output from the crash accelerometer.
Such crash sensor pulse samples obtained from the sensor prototype tests at various speeds and test modes for vehicle sensor calibrations and development are very expensive and time consuming. For each speed at which a test is executed there is destructive testing of a prototype vehicle and crash sensor. Using computer aided engineering (CAE) methods to predict the crash sensor pulses are also unreliable because of the high sensitivity of structural complexity on high frequency band of response. These are some of the problems this invention overcomes.
This method generates a calibration crash sensor output pulse at a plurality of crash speeds from the combination of a generated high frequency band pulse output (HFB) and a generated low frequency band pulse output (LFB). Destructive testing is not necessary to generate the calibration crash sensor output pulse at a plurality of crash speeds. The calibration crash sensor output pulses can then be used to test an air bag firing control module for proper operation. That is, when vehicle crash conditions are met, the firing control module should produce an air bag firing signal. As a result, air bag system development is simplified.
The HFB pulse is an elastic wave, which travels along a vehicle system at the speed of sound and is sensitive to impact location and system complexity such as joints, mounts, and other components. The LFB pulse is a non-elastic wave that depends on vehicle system stack-up and crush deformation.
The LFB pulse can be obtained from traditional finite element analysis or lumped masses model analysis. Such models are typically created during production of a vehicle prototype and are well known in the art. This invention recognizes that such CAE methods can be advantageously used in to generate a LFB pulse component of a calibration crash sensor output pulse.
The HFB pulse normally is difficult to be predicted by CAE methods. The inventive method uses either of two options to obtain the high frequency band pulse. A first option uses a nondestructive test to obtain the HFB pulse at low vehicle speed and then uses a linear transformation method to convert the HFB of low vehicle speed to other HFBs of other higher vehicle speeds. A second option uses only the highest vehicle crash speed test crash sensor output to obtain the HFB pulse and then uses a linear transformation method to convert the one highest crash speed test crash sensor output HFB pulse to the HFB pulses of other lower crash speed test crash sensor outputs.
Once the LFB and HFB pulses are obtained, the crash sensor calibration output pulse can be constructed by combining the two frequency band pulses. The crash sensor calibration output pulse can then be used to test the response of an air bag firing module. When a calibration crash sensor pulse indicating a crash event when air bag firing is required is received by an air bag firing module, an air bag firing signal should be generated by the air bag firing module. On the other hand, if the calibration crash sensor pulse is a type that does not require air bag module firing, the air bag firing module should not generate an air bag firing signal.
Accordingly, a significant advantage of this invention is the ability to avoid destructive testing. As discussed, crash sensor pulse samples obtained from the sensor prototype tests at various speeds and test modes for vehicle sensor calibrations and development are very expensive and time consuming. For each speed at which a test is executed there is destructive testing of a prototype vehicle and crash sensor. Using computer aided engineering (CAE) methods to predict the crash sensor pulses may lack reliability in some cases because of the high sensitivity of structural complexity in the high frequency band of response. These are some of the problems this invention overcomes.